1. Field of the Invention
This invention relates to a metal respirator cartridge of the type containing a particulate filter, and more particularly to a metal cover allowing the periphery of the particulate filter to be sealed to the cartridge body.
2. Description of the Prior Art
An essential step in the manufacture of a respirator cartridge, whether it is a filter cartridge or a combination chemical/particulate filter cartridge, is the encapsulation of the filter. That is the periphery of the filter is sealed against the metal cartridge body by means of a liquid sealant, such as, a two-component urethane compound which hardens as it cures. The peripheral sealing is necessary to ensure that air flowing through the cartridge, actually flows through the filter and does not bypass the filter.
Heretofore, the encapsulation of filters in metal cartridge bodies, was accomplished by means of a silicone mold or boot which was used during the encapsulating process and prior to final assembly of the cartridge. Typically, a particulate filter is placed in the metal cartridge body followed by the silicone boot. The silicone boot sits in the cartridge body and serves to control the height of the sealant wall formed at the periphery of the filter and, most importantly, to confine the sealant within the cartridge. Thereafter the cartridge/boot combination is rotated at at least 500 rpm and liquid sealant is then dispensed into the boot. The centrifugal forces created during the high speed rotation of the cartridge/boot combination, cause the liquid sealant to flow inwardly of the boot and outwardly to the periphery of the particulate filter to form a sealant wall of substantially uniform thickness between the inner wall of the cartridge body and an outer portion of the filter. After the sealant sets or hardens, spinning is stopped, the boot is removed and assembly of the cartridge continues.
From start to finish, the process of encapsulating and assembling each metal respirator cartridge, is longer than desirable, is considerably messy, and more costly. It has been found that after twenty (20) to twenty-five (25) uses, the silicone boot becomes unusable due to the accumulation of excess sealant and other debris. Since cleaning the boot is a time consuming and uneconomical operation, the boot typically is discarded and a new boot is used in encapsulating the next series of cartridges.